Intensity rate of change control for musical instruments



Oct. 29, 1963 M. CLARK, JR 3,109,047

INTENSITY RATE OF CHANGE CONTROL FOR MUSICAL INSTRUMENTS Filed April 1,1960 SOUND REPRODUCING SYSTEM INVEN TOR.

MELVILLE CLARK JR.

ATTORNEYS United States Patent ()flice 3,109,047 Patented Oct. 29, 19633,109,047 INTENSITY RATE OF CHANGE CONTROL FOR MUSICAL INSTRUMENTSMelville Clark, Jr., 17 Bellvue St-, Newton 58, Mass. Filed Apr. 1,1960, Ser. No. 19,304 7 Claims. (Cl. 84-1.27)

The present invention relates in general to electronic musicalinstruments and more particularly concerns a novel circuit forcontrolling the rate of change of sound level. A performer may control amusical instrument incorporating the invention to produce desiredmusical effects by changing the rate for attaining a new intensity. Theapparatus embodying the invention is relatively low in cost, easy toconstruct and reliable in operation.

Many musical compositions include passages where changes in theintensity of the music should occur at a predetermined rate. This goalis generally accomplished by each individual performer graduallychanging the sound intensity emitted by his own instrument. While themost highly skilled musicians usually effect such changes smoothly,musicians of lesser skill exercise more erratic control and the soundsthey produce during such changes in level are less pleasing.

Accordingly, the present invention has as an important object theprovision of means for manually or pedally selecting the rate at whichthe intensity of electronic instrument music is changed and effectingsuch change so smoothly that even a mediocre or poor musician producespleasant-sounding level changes.

It is still another object of the invention to achieve the precedingobject with a low cost reliably operating apparatus that is relativelyeasy to fabricate.

According to the invention, a variable gain amplifier receives a musicalsignal at its input and delivers the amplified signal to a soundreproducing system. A gain control signal establishes the amplifiergain, an associated electrical circuit initially resisting changes inthe gain control signal when a parameter of the circuit is changed.Means mechanically coupled to the circuit change the parameter, causingthe gain control signal to approach a new steady-state value at a ratedetermined by the circuit.

In an exemplary embodiment of the invention, the circuit comprises meansincluding a variable resistance for selectively direct coupling acapacitor to a source of direct potential so that the gain controlsignal is developed across the capacitor. A rate pedal is linked to amovable arm which selectively contacts a resistor at different points.As the musician moves the pedal from a neutral position with the armfloating, the arm contacts the resistance to progressively decrease theresistance in series with the source, thereby correspondingly increasingthe rate of intensity change.

Numerous other objects, features and advantages of the invention willbecome apparent from the following specification when read in connectionwith the accompanying drawing.

The single FIGURE of the drawing shows a combined block-schematiccircuit diagram of a musical instrument according to the invention.

.With reference now to the drawing, a musical signal provided by thesource 11 is amplified by the variable gain amplifier comprising tube V1and associated circuit components and reproduced by the soundreproducing system 12 which converts the electrical music signals tosound energy.

Tube V1 may be a sharp cut-off pentode which receives the musical signalfrom source 11 on its grid. A grid resistor 13 direct-couples the gridto the arm 14, shown in its normal neutral posititon unconnected toeither of resistors 15 and 15. Resistors 15 and 15 are connectedrespectively to a source of negative potential on terminal 16 and asource of positive potential on terminal 17. The potential acrosscapacitor 21 selects the grid bias for tube V1 and controls thetransconductance of this tube which in turn determines the gain of theassociated amplifier. Thus, the circuit components which establish thegrid bias for tube V1 represent a source of a gain control signal. Thistiming capacitor 21 is connected between the arm 14 and ground, thesteady-state potential across this capacitor with arm 14 in the neutralposition being zero due to the leakage resistance of the physicalcapacitor itself. However, the quasi steady st-ate potential across thiscapacitor is the potential which existed across the capacitor justbefore the arm 14 was returned to the neutral position. This potentialdrifts to zero very slowly because the time constant of the capacitor 21and its leakage resistance is very large, it being understood thatsource 11 presents a high impedance D.-C. path to ground through the useof a coupling capacitor (not shown) in series with the junction of thegrid of tube V1 and resistor 13, for example.

A rate pedal 22 is attached to the musical instrument and a mechanicallinkage 2'3 mechanically couples the pedal 22 to the arm 14, the armposition being selected by positioning the pedal 22.

Tube V1 is otherwise connected as a conventional pentode amplifier whichmay have a small unbypassed resistor 24 in the cathode circuit toincrease stability and lessen distortion. A plate load resistor 25 isconnected between the plate and a source of positive potential onterminal 26. The screen grid receives its potential through a screendropping resistor 27 and is bypassed to ground by an electrolyticcapacitor 28. {The signal on the plate of tube V1 is delivered to thesound reproducing system 12.

Operation is as follows. The arm 14 normally resides in a neutralfloating position. The steady-state potential on the grid of tube V1 isthen substantially zero to establish a normal gain for the amplifier. Ifthe pedal 22 is depressed, the arm 14 moves toward the right, causingcapacitor 21 to charge to the potential on terminal 17. Capacitor 21prevents the grid bias from changing instantaneously. However, the rateof change in bias and consequently amplifier gain is determined by thetime constant of the capacitor 21 with the fraction of resistance 15'through which it charges. If the pedal position change is great, thechange in the sound level will occur rapidly but smoothly while a slightchange in pedal position is accompanied by a smooth slow change involume.

The specific embodiment described herein is by way of example only. Itis evident that those skilled in the art may employ other types ofamplification devices and networks of different form for effecting thedesired control of the rate of change of intensity. Numerous othermodifications of and departures from the specific em bodiment describedherein may be practiced by those skilled in the art without departingfrom the inventive concepts. Consequently, the invention is to beconstrued as limited only by the spirit and scope of the appendedclaims.

What is claimed is:

l. An intensity rate of change control for -a musical instrumentcomprising, a variable gain amplifier having a signal input and a signaloutput, a source of a gain control signal, means for coupling said gaincontrol signal to said amplifier to establish the amplifier gain, anelectrical circuit associated with said source for initially resistingchanges in said gain control signal when a parameter of said circuit ischanged, means mechanically coupled to said circuit for changing saidparameter and selecting a new finite value for said gain control signalwhich the latter approaches at a rate determined by said parameter,

and means for maintaining the new selected value of said gain controlsignal when that new value is reached.

2. Apparatus in accordance with claim 1 wherein said circuit comprises,an adjustable arm, a source of direct potential, a capacitor connectedto said arm, and a resistor connected to said source of directpotential, said gain control signal being developed across saidcapacitor, said arm being selectively connectable to different points ofsaid resistor in response to actuation of said mechanically coupledmeans.

3. Apparatus in accordance with claim 2 wherein said mechanicallycoupled means comprises a pedal and further comprising, a linkagebetween said pedal and said arm for causing said pedal and said arm tomove together. a

4. Apparatus in accordance with claim 3 wherein said amplifier comprisesan electron tube whose transconductance is a function of its grid bias,and a resistor connected between the grid of said electron tube and saidarm, the potential across said capacitor thereby establishing said gridbias.

5. In an electrical musical instrument, apparatus for controlling therate of change of music intensity comprising, a source of an electricalmusical signal, variable gain amplifying means responsive to saidelectrical musical signal for providing an output signal, transducingmeans responsive to said output signal for providing correspondingpressure variations, a capacitor, means for coupling the potentialacross said capacitor to said amplifying means to control the gainthereof, a source of a fixed potential, resistive means connected tosaid fixed potential source, a movable arm for selectively exchangingcharge between said capacitor and said source through said resistivemeans, the resistance of the latter between said fixed potential sourceand said capacitor being related to the position of said arm along apath including points of contact with said resistive means, whereby saidcapacitor charges toward said fixed potential at a rate determined bythe time constant of said resistance and said capacitor, means forcontrolling movement of said arm along said path, said path including aneutral position disconnected from said resistive means, and means formaintaining said arm in said neutral position to then maintain said gainat a value determined by the potential on said capacitor at the timesaid arm is moved to said neutral position.

6. Apparatus in accordance with claim 5 wherein said amplifying meanscomprises a remote cutoif electron tube, the grid bias of said tubebeing related to the potential across said capacitor, said time constantbeing large compared to the period of a low audio frequency.

7. Apparatus in accordance with claim 6 wherein said time constant isgreater than one second.

References Cited in the file of this patent UNITED STATES PATENTS2,226,259 Richards et al Dec. 24, 1940 2,516,556 Duke July 25, 19502,555,295 Schmidt May 29, 1951 2,578,541 Hammond Dec. 11, 1951 2,695,386Schmidt Nov. 23, 1954 2,918,576 Munch Dec. 22, 1959

5. IN AN ELECTRICAL MUSICAL INSTRUMENT, APPARATUS FOR CONTROLLING THERATE OF CHANGE OF MUSIC INTENSITY COMPRISING, A SOURCE OF AN ELECTRICALMUSICAL SIGNAL, VARIABLE GAIN AMPLIFYING MEANS RESPONSIVE TO SAIDELECTRICAL MUSICAL SIGNAL FOR PROVIDING AN OUTPUT SIGNAL, TRANSDUCINGMEANS RESPONSIVE TO SAID OUTPUT SIGNAL FOR PROVIDING CORRESPONDINGPRESSURE VARIATIONS, A CAPACITOR, MEANS FOR COUPLING THE POTENTIALACROSS SAID CAPACITOR TO SAID AMPLIFYING MEANS TO CONTROL THE GAINTHEREOF, A SOURCE OF A FIXED POTENTIAL, RESISTIVE MEANS CONNECTED TOSAID FIXED POTENTIAL SOURCE, A MOVABLE ARM FOR SELECTIVELY EXCHANGINGCHARGE BETWEEN SAID CAPACITOR AND SAID SOURCE THROUGH SAID RESISTIVEMEANS, THE RESISTANCE OF THE LATTER BETWEEN SAID FIXED POTENTIAL SOURCEAND SECOND CAPACITOR BEING RELATED TO THE POSITION OF SAID ARM ALONG APATH INCLUDING POINTS OF CONTACT WITH SAID RESISTIVE MEANS, WHEREBY SAIDCAPACITOR CHARGES TOWARD SAID FIXED POTENTIAL AT A RATE DETERMINED BYTHE TIME CONSTANT OF SAID RESISTANCE AND SAID CAPACITOR, MEANS FORCONTROLLING MOVEMENT OF SAID ARM ALONG SAID PATH, SAID PATH INCLUDING ANEUTRAL POSITION DISCONNECTED FROM SAID RESISTIVE MEANS, AND MEANS FORMAINTAINING SAID ARM IN SAID NETURAL POSITION TO THEN MAINTAIN SAID GAINAT A VALUE DETERMINED BY THE POTENTIAL ON SAID CAPACITOR AT THE TIMESAID ARM IS MOVED TO SAID NETURAL POSITION.